My third post on African languages in the UNESCO year of indigenous languages looks at a particular type of multilingualism that is extremely rare in the West. All over Africa (and in other areas of the world where Deaf people do not receive specialized education separate from hearing learners), hearing and Deaf people form speech communities where hearing and non-hearing members share sign languages. These sign languages are often specific to particular locations and not related to the widely distributed national and international sign languages such as American Sign Language (ASL). In contrast to most Western settings, where education is focussed on acquiring spoken and written language, and where communication in sign languages is mainly limited to Deaf people and their families, Deaf people in these settings are fully integrated into their local communities. Their hearing members are often multilingual in several spoken languages but also master and pass on the sign language. The extent to which sign languages in these settings are conventionalized and in which communicative contexts they are used depends on the size and time-depth of the community. You can read an account of village sign communities in rural Mali here:

Nyst, Victoria, Sylla, Kara & Magassouba, Moustapha (2012) Deaf signers in Douentza, a rural area in Mali In: Zeshan, Ulrike and Connie de Vos eds. 2012. Sign languages in village communities: Anthropological and linguistic insights. Sign Language Typology Series 4. Berlin: Mouton de Gruyter. 

If you want to have a look at how sign language is shared with hearers in a setting where it is not highly conventionalized (because there is only a single Deaf person), have a look at this blogpost and video situated in the village Djibonker in Senegal by Mia Weidl and Andrés Carvajal.